Dry cleaning process



United States Patent 3,396,115 DRY CLEANING PROCESS William R. Moore, Lake Jackson, Tex., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Filed Aug. 12, 1965, Ser. No. 479,291 3 Claims. (Cl. 252171) ABSTRACT OF THE DISCLOSURE Dry cleaning solvents are provided with detergent properties and other beneficial characteristics when there is dissolved in them a small but effective amount of a polysulfone resin resulting from the copolymerization of sulfur dioxide and an alpha monoolefin of 630 carbon atoms.

This invention relates to a new and improved process for dry cleaning textile fibers, cloth, and similar fibrous materials. The invention relates particularly to a novel application of a polymeric resin as a dry cleaning detergent whereby superior results are produced.

In conventional dry cleaning processes for the removal of dirt and grease from textile fibers, fabrics, and garments formed thereof, use is made of a liquid dry cleaning bath which consists essentially of a dry cleaning solvent having dissolved in it a minor proportion of a detergent. The bath may also contain small quantities of other additives such as water, antistatic compounds, textile softeners, or water repellents.

Solvents commonly used as the base of such compositions include saturated aliphatic hydrocarbons such as ligroin, gasoline, Stoddard solvent, or other low-boiling parafiin hydrocarbons and mixtures thereof; benzene, toluene, xylene, and other low-boiling aromatic hydrocarbons or mixtures thereof; and particularly, low-boiling polyhalogenated hydrocarbons of 1-2 carbon atoms such as carbon tetrachloride, methylchloroform, ethylene dichloride, trichloroethylene, tetrachloroethylene, trichlorofluoromethane, dichlorotrifluoroethane, trichlorodifluoroethane, and mixtures of these.

Anionic, cationic, and nonionic detergents have been and are used as the detergent component of such dry cleaning baths. As examples of these there may be mentioned alkali metal or ammonium higher alkyl sulfates and sulfonates, similar salts of higher alkylbenzenesulfonic acids, phosphate esters, higher alkyl quaternary ammonium halides, and adducts obtained by reacting -15 molecules of ethylene oxide with a molecule of an alkylphenol, a higher alcohol, or a higher fatty acid or amide thereof. Inorganic detergents such as alkali metal phosphates, polyphosphates, and metaphosphates have also been employed. Most of these compounds have one or more objectionable characteristics such as high cost, poor cleaning efiiciency at low concentrations, color, or unpleasant odor.

It has now been found that unexpectedly eflicient cleaning and other valuable results are obtained when the detergent component of a dry cleaning bath such as described comprises a polysulfone which is the substantially linear copolymer of sulfur dioxide and an alpha olefinic hydrocarbon of about 6-30 carbon atoms. Polysulfones of the class described having an average molecular weight of at least 5 10 and preferably about 1 10 2 10 are suited to the practice of this invention.

A particular advantage of the present process is the relatively low concentration of polysulfone required to obtain effective cleaning. Whereas detergents are normally present in conventional dry cleaning solutions in concentrations of at least g. per liter, the most effective polysulfone concentrations lie in the range of 1-20 g.

3,396,115 Patented Aug. 6, 1968 per liter. Polysulfone concentrations as low as 0.1 g. per liter of solvent provide significant cleaning while as much as 50 g. of polysulfone per liter of solvent may be employed without unduly increasing the viscosity of the cleaning solution.

In some cases it may be desirable to employ these polysulfones in combination with a conventional detergent or with other known dry cleaning additives, for example, an antistatic compound. Small proportions of water, e.g., up to about 650 ppm. by weight of the solvent, may be included to maintain a desired level of humidity in the system.

The use of these polysulfone resins as dry cleaning detergents confers other benefits on the cleaned fibers, fabrics, or garments. Material cleaned by such a bath is soft to the touch and somewhat water-repellent. The po1y sulfones also impart wrinkle-resistance to cleaned fabrics and leave no residual odor.

Copolymers of sulfur dioxide and alpha olefins, commonly referred to as polysulfones, can be prepared by any of various methods described in the published literature as exemplified by U.S. Patents 2,136,389 and 2,602,787 and by Snow et al., I. Am. Chem. Soc. 65, 2417 (1943).

Polysulfones suitable for the practice of this invention are those resulting from the copolymerization of sulfur dioxide and alpha olefins in the approximate range of 6- 30 carbon atoms per molecule. The alpha olefins should be predominantly between C and C preferably C C although minor amounts of lower molecular weight alpha olefins may be present. Since the polysulfones which are useful in this invention are of substantially linear molecular structure, the olefin starting material must be essentially free of diolefins or other polyfunctional crosslinking compounds.

The polymerization is carried out in the liquid phase normally at about ambient temperature, employing a molar excess of sulfur dioxide to olefin, preferably about 2-30/1. An inert solvent such as hexane, benzene, kerosene or water may be employed.

The polymerization is initiated by radiation such as actinic light or high energy radiation or by various chemical catalysts. High energy radiation such as gamma rays and accelerated electrons is suitable and this may be supplemented by a chemical catalyst. Among known chemical catalysts are ionic catalysts such as silver nitrate, ammonium nitrate, lithium chlorate, and the like, and peroxy free radical initiating compounds such as hydrogen peroxide and methyl ethyl ketone peroxide. Suitable catalysts concentrations are 0.001-0.5 percent of an ionic catalyst or 0.05-5 percent of a peroxide catalyst based on the weight of alpha olefin.

The polysulfone resins thereby obtained are white solids having a molecular weight in excess of 5 X 10 and usually in the approximate range of 1X 10 to 2x10 They are more or less soluble in the common organic solvents, insoluble in water and aqueous solutions.

The following examples demonstrate the cleaning efliicency of the new process, particularly as compared to processes employing conventional solvent-detergent compositions. In these examples, the reflectance values which are used to measure cleaning efficiency are averages obtained from several test swatches in each case.

Example 1 Standard carbon-soiled 4 x 6 inch swatches of wool cloth were put in each of four tubs of a drycleaning test apparatus, each tub containing one liter of perchloroethylene plus detergent as noted. The swatches were agitated for 30 minutes at rpm. stirrer speed and at room temperature. The swatches were then air-dried at 23 C. and their reflectance values were determined with a Photovoltmeter Reflectometer. These values are compared with reflectances similarly obtained from the soiled swatches.

1 Perehloroethylene containing 20 g. per liter of sodium alkanesulfonate of 20-24 carbon atoms.

2 016-20 alpha olefin polysulfone of 600,000 avg. mol. wt.

'Polysulfones of average molecular weights as shown were prepared by reacting sulfur dioxide with C alpha olefin and C1630 alpha olefin fractions respectively in Water containing 0.8% sodium lauryl sulfate as emulsifier and 0.8% ammonium nitrate as reaction catalyst. Perchloroethylene baths containing -1.5 g. polysulfone per liter were used to clean carbon-soiled 4 x 6 inch swatches of wool cloth as shown in Example 1 and the reflectance values of the cleaned and dried swatches were determined, also as described in that example. The dry cleaning efliciency of each of these polysulfones is shown by the resulting data listed below.

Swatch Reflectance Cleaned Percent Gain 1 C a-olefin polysulfone of 600,000 avg. mol. wt.

2 O a-olefin polysulfone of 186,000 avg. mol. wt.

3 018-20 a-olefin polysulfone of 369,000 avg. mol. wt.

4 016- a'olefin polysulfone of 1,020,000 avg. mol. wt.

Example 3 The anti-soil redeposition properties of the polysulfone of Example 1 and commercial detergents in perchloroethylene systems were compared by a procedure similar to that of the foregoing example. Clean 4 x 5 inch worsted gabardine swatches were agitated at room temperature for 30 minutes in separate tubs containing one liter portions of matured perchloroethylene solution, each solution containing an estimated 10 g. per liter of natural particulate soil and detergent as noted. Reflectances of the swatches were measured before and after treatment as previously described and the differences were calculated as percentages of the original reflectance values.

Mixed alkoxypolyethyleneoxyethanol mono and di esters of phosphoric acid, an anionic detergent.

-Nonylpheuol-ethylene oxide adduct containing about 9 moles EO/mole of phenol, a. nonionic detergent.

Example 4 The procedure of Example 3 was repeated using swatches of clean bleached cotton print cloth. The polysulfone was that previously used.

Detergent: Percent loss of reflectance None 7.8 100 g./ liter Dowfax 9N9 8.4

5 g./liter polysulfone 6.6

Example 5 A commercial coin-operated dry-cleaning machine was thoroughly cleaned, loaded with clarified powders as per manufacturers instructions, and charged with 18.5 gallons of freshly distilled perchloroethylene containing 190 g. (2.7 g./liter) of a polysulfone of 600,00 average molecular weight obtained by copolymerizing S0 and an alpha olefin fraction of about 16-20 carbon atoms average chain length.

A total of nine 8 lb. loads of naturally soiled clothes were cleaned, each containing .6 x 6 inch test swatches of cotton, wool gabardine, wool flannel, spun acetate rayon, and viscose taffeta rayon. Each load also contained a 4 x 6 inch carbon-soiled wool swatch of the type used in Example 1.

Swatch reflectance readings before and after the cleaning operation were taken as described in Example 1.

Reflectance Reading It was found in addition from the above tests that the cleaned clothes were softer and more wrinkle-resistant than before cleaning. A degree of water repellency had also been imparted to the cleaned garments by the polysulfone.

The low color of a polysulfone dry-cleaning solvent solution as compared to similar commercial solvent compositions is an advantageous feature of the present invention. A typical comparison is shown by the following table of data relating to perchloroethylene solutions.

In this table, the Klett color values indicate the relative optical densities of the respective solutions. The polysulfone was that used in Example 5.

TABLE 1 Solvent composition: Klett color Pure perchloroethylene 0 C Cl +20 'g./liter Na alkanesulfonate C Cl +l0 g./liter polysulfone 0 C Cl +50 g./liter polysulfone 3 I claim:

1. In a dry-cleaning process wherein fibrous materials are washed in a bath comprising a dry-cleaning solvent and a detergent, the improvement wherein said detergent comprises Oil-50 grams per liter of solvent of a linear polysulfone copolymer of sulfur dioxide and an alpha olefin of 6-30 carbon atoms, said polysulfone having an average molecular weight of 5 X 10 to 2x10 2. The process of claim 1 wherein the dry-cleaning solvent consists essentially of perchloroethylene.

3. The process of claim 2 wherein the detergent consists essentially of 1-20 grams of polysulfone per liter of perchloroethylene.

References Cited UNITED STATES PATENTS 2,136,389 ll/1938 Marvel et al. 260-7 9.3 2,602,787 7/1952 Crouch 260-793 2,853,373 9/1958 Stuart 4462 LEON D. ROSDOL, Primary Examiner.

J. FEDIGAN, Assistant Examiner. 

